On the Delicious Brains site they've posted a tutorial that provides some helpful tips and tricks for optimizing your SQL queries on your WordPress sites with the help of some basic techniques and software to analyze your current use.

With dynamic database-driven websites like WordPress, you might still have one problem on your hands: database queries slowing down your site.

In this post, I’ll take you through how to identify the queries causing bottlenecks, how to understand the problems with them, along with quick fixes and other approaches to speed things up. I’ll be using an actual query we recently tackled that was slowing things down on the customer portal of deliciousbrains.com.

They then walk through some of the methods for locating the queries that could be causing issues including the use of the QueryMonitor plugin and the MySQL slow query log. They provide some tips for understanding what makes the query slow and how to use the MySQL Workbench tool to determine the structure of the database and look for optimizations. Finally they get into some of the things they did to solve their own issue including adding caching, better understanding the need of the query and "thinking outside the box" with indexes and normalization.